#-*- codeing = utf-8 -*-
#@Time:2022/9/1214:20
#@Author :计科1813-14-张玉婷
#@File:2.1.py
#@Software:PyCharm


x=int(input("请输入百分制成绩X的值："))
if x>=90:
    print("A")
elif x>=80:
    print("B")
elif x>=70:
    print("C")
elif x >= 60:
    print("D")
else:
    print("E")